650 



COMPENDIUM OF GENERIC DISTINCTIONS. 



Genus. — Arvicola. 



Teeth.— I. 



M. 



= 16. 



Molars curiously 



y P h 1 

 i— i' ' i— i" 



folded so as to form a double series of triangles on their crowns. 

 Head. — Ears rounded and very short. 

 Limbs. — Feet as in Mus, soles without hair. 

 Tail. — Rather short. 

 Habitat. — Europe. 



Genus. — Myodes. 

 Teeth, as in Arvicola. 

 Head. — Ears not visible beyond the fur. 

 Limbs. — Feet with soles hairy, fore-feet with digging claws. 

 Tail. — Very short, covered with hair. 

 Habitat. — Norway and Sweden. 



Sub-family. — Castorina. 



Teeth. — Incisors covered with colored enamel, and smooth in 

 front. Molars with four folds of enamel. 

 Limbs. — Feet with five toes, hinder feet webbed. 

 Head. — Ears small and round. 



Teeth.— I. 



= 20. 



Genus. — Castor. 



i,p.y,n» 



1—1 1—1 3—3 



Limbs. — Hind-feet entirely webbed. 

 Tail. — Wide, flat, and covered with scales. 

 Habitat.— North America and part of Europe. 



Genus. — Myoputamus. 

 Teeth, as in Castor. 



Limbs. — Only four toes of hind-feet webbed. 

 Tail. — Round and hairy. 

 Habitat.— Chili. 



Genus. — Fiber. 



Teeth.— I. 



= 16. 



*=!, P. 1=1, M . ?Z» 

 1—1 1—1 2—2 



Limbs. — Claws curved and flattened. Toes of hinder feet long, 

 and edged with thick, stiff hairs. 



Tail. — Moderate and compressed, a few short hairs appearing 

 through the scales with which it is covered. 

 Habitat. — North America. 



Genus. — Hydromys. 



Teeth.— I. — , P. — , M. — = 12. 



1—1 1—1 1-1 



Limbs. — Hinder feet partially webbed. 

 Tail. — Round, hairy, and large at the base. 

 Habitat. — New Holland and Van Diemen's Land. 



Sub-family. — Echimyna. 

 Teeth. — Incisors straight, and abrupt at their extremities. 



Genus. — Aulacodus. 



Teeth. — Incisors broad and short, brown in front, three furrows 

 in those of the upper jaw. Molars with four folds of enamel. 



Limbs. — Fore-feet with thumb and outer toe short. Hind-feet 

 with four toes. 



Tail. — Rather short, slightly covered with hair. 



Fur. — Composed of flattened and grooved hair, or grooved 

 spines. 



Habitat. — Southern Africa. 



Family. — HTSTBtciD^:. 



Teeth. — Incisors smooth and large ; molars with waving strips 

 4--t 



of enamel, always 



4-4 



Limb3. — Fore-feet with four toes, a wart instead of the thumb- 

 joint. 

 Fur.— None, being replaced by strong and sharp spines. 



Sub-family. — Hystrkina. 



Teeth. — Molars with undivided roots, set deeply in the bone j 

 third molar placed under the anterior margin of the orbit. 

 Limbs. — Feet with soles smooth, but grooved. 



Genus. — Hystrix. 



Limbs. — Hind-feet with five toes. 



Tail. — Not prehensile. 



Habitat. — Parts of Europe, Africa, and Asia. 



Atherura is included in this genus. 



y 

 Sub-family. — Gercolabina. 



Teeth. — Molars with short, divided roots, set shallow in the 

 bone. First molar placed under margin of orbit. 

 Limbs. — Feet with warty soles. 



Genus. — Erethizon. 



Tail. — Short and spined. 



Limbs. — Hind-feet with five toes. 



Fur. — Long hair, interspersed with short, sharp spines. 



Habitat. — Canada. 



Genus. — Cercolabes. 



Tail. — Long and prehensile. 

 Limbs. — Hind-feet with four toes. 

 Habitat. — Brazils. 



Sub-family. — Subunguldta. 



Teeth. — Molars complex. 



Limbs. — Fore-feet with four or five toes, hind-feet with three 

 or four. Claws large and keeled above. 



Genus. — Dasyprocta. 

 Head. — Lips cloven. 



Limbs. — Fore-feet with four toes and a wart for the thumb ; 

 hind with three toes. 

 Tail. — Represented by a small, naked tubercle. 

 Fur. — Hair long on hind-quarters. 

 Habitat. — Brazils. 



Genus. — Ccelogenys. 



Head. — Lip cloven. Great development of zygoma, lined with 

 a fold of skin. Cheek-pouches. 



Limbs.— Fore-feet with four toes and nailed wart for thumb. 

 Hind-feet with three toes. 



Tail. — Very short. 



Habitat. — Tropical America. 



Genus. — Hydrochcerus. 



Teeth.— Slight longitudinal groove on upper incisors. Molars 

 without roots. 



Head. — Thick, lips not cleft. 



Limbs. — Feet partially webbed. Fore-feet with four toes, 

 hinder with three. 



Tail.— None. 



Habitat. — Tropical America. 



Genus. — Cavia. 



Molars without roots 



aud curiously 



four toes, hinder with 



Teeth. — Incisors smooth 

 laminated. 



Head. — Ears short and rounded. 



Limbs. — Feet cloven; fore-feet with 

 three ; feet short. 



Tail.— None. 



Habitat. — Brazils. 



Family. — Lep6ktd.«:. 



Teeth. — Four incisors in upper jaw, a pair of these teeth being 

 placed behind the two usual incisors. Molars without roots, 

 formed of two laminas. 



Limbs. — Fore-feet with five toes, hinder with four ; soles hairy. 



Tail. — Short, ©r absent. 



